INES Mapper 155

iNES Mapper 155 is assigned to games that require the MMC1A variant of the MMC1. Unlike MMC1B and MMC1C, MMC1A lacks the WRAM disable bit in the PRG bank register ($E000-$FFFF). Games that use this mapper write values between $10 and $1F to the PRG bank register, write to WRAM at $6000-$7FFF, and require the write to succeed.

According to the database shipped with Nestopia 1.4.0, these two Famicom games require this behavior:

Either this was done as a copy protection mechanism or the programmers just weren't aware that later MMC1 revisions would add a bit for disabling WRAM.

Technically, these two games are on SKROM and SJROM, and so theoretically this mapper should not have to implement any of the boards that repurpose PRG or CHR pins (SE-, SH-, SN-, SO-, SU-, SX-ROM). However, it is probably still wise to pay attention to the caveats said here.